A serious problem associated with turbine pumps and their rotating parts is the overheating of the bearings in which the parts rotate. Bearing overheating can result from the interruption of the flow of lubricating oil due to particle contamination of the needle valve or ambient temperature change.
In a typical pump system, the lubricating oil is gravity fed from an oil container drum and regulated through a sight gauge by an adjustable needle valve to provide a flow of approximately 6 to 8 drops per minute for each 100 feet of pump length. It is delivered to the stretch bearing at the top of the well though a 1/4" copper tube and then through grooves cut in the line shaft bearings, which are spaced at five foot intervals, all the way down to the bottom of the well where the pump bowl is located. The needle valve regulator is sensitive to moisture, dust and various foreign particles, all of which are present in the atmosphere in certain environments, and all of which cause clogging in the needle valve. Oil flow interruption can also be caused by a drop in ambient temperature. As the ambient temperature declines, the viscosity of the lubricating oil flowing from the oil container drums increases. The colder the temperature becomes, the thicker the oil becomes, and the slower the oil flows through the needle valve. When the ambient temperature has declined sufficiently, the oil becomes so thick that it cannot pass through the needle valve and onto the pump line shaft and bearings. Oil flow to the line shaft and bearings can also be terminated by the pump operator's failure to keep a supply of oil in the oil reservoir. The consequent loss of oil flow causes increased friction which, in turn, permits the pump shaft and bearings to overheat.
After the lubricant flow interruption, temperatures in the line shaft may exceed the flash point of the oil used to lubricate the line shaft and bearings, causing residual oil in the shaft to vaporize. If the pump continues operation thereafter without lubrication, the bearing temperature will continue to rise, causing the bearings to experience massive wear very quickly and to flake off into the oil tube and onto the bearings below. Flaking of a bearing plugs up the oil transport groove in the bearing immediately below the flaking bearing, and, thereby, permanently stops oil flow to the bearings further down the line shaft, which results in pump shaft failure.
Pump shaft failure involves expensive repairs and loss of service while the well is down. In agriculture, crucial periods in crop growth require a constant supply of irrigation water; consequently, any significant loss of water supply at such times results in partial or complete crop failure.
Prior art patents offer some suggestions for dealing with the problem of bearing failure resulting from excessive temperature. Heckert (U.S. Pat. No. 2,089,369) described an overheated bearing and journal detection and identification system associated with wheel axles of railway cars. Heckert's heat detection system relied on the melting point of a fusible closure disk immediately associated with a journal box and bearing.
Others have resorted to the use of various temperature sensing means imbedded in the bearing itself, or, alternatively, in the bearing housing support to detect and monitor bearing temperatures (Waseleski et al., U.S. Pat. Nos. 3,824,579; Bergman et al. 4,074,574; Gustafson 3,052,123; Reumund 2,964,875). However, because bearings associated with turbine pumps are located within oil tube line shaft encasements surrounded by flowing fluid, such as water or oil, temperature sensors embedded in such bearings may be inaccurate and their temperature readings unreliable. Even the flow of fluid below the bearing affects the temperature perceived by a sensor embedded in the bearing. Sometimes a packing heats up instead of a bearing, but a sensor imbedded in the bearing is not sensitive to the packing temperature, and it is not practical to embed a sensor in the packing.
Devices and methods for detecting bearing overheating using infrared sensors have also been considered. Gallagher (U.S. Pat. No. 5,448,072) teaches a means of determining hot bearings and hot wheels of a train by monitoring the end caps of train wheels with an infrared scanner. Gallagher determined that the temperature of the end caps gives an accurate indication of the bearing temperature. Duhrkoop (U.S. Pat. No. 5,478,151) teaches a device for detecting overheated bearings in rail cars and other moving objects using an infrared beam detector and multiple lenses, each one of which is aimed at a different measuring point, and a scanning device which periodically picks up the measuring beams and focuses the beams onto the detector. The patents discussed above are directed toward overheating of bearings in railroad cars.
Because the bearings in a pump system are located either within the pump casing or within the oil tube, which descends deep into the ground, determining overheating in pump bearings presents unique problems. However, it has been discovered that the stretch bearing, which is located in the pump head and positioned on the pump line shaft above the level of fluid flow through the pump column and discharge head, overheats and fails first.
Senior, Jr. et al (U.S. Pat. No. 5,145,322) teaches a device and method for detecting overheating in deep well water pump bearings by placing a temperature probe in a bore drilled in the stretch bearing and opening into an air space communicating between the oil inlet chamber below the dust seal packing and the oil tube space. Although Senior teaches an effective means of detecting bearing overheating, it requires retrofitting an existing pump to accommodate the device. Retrofitting an existing pump requires partially disassembling the pump, which further requires machinery and man power.